The nearly one million cesarean deliveries performed in this country each year are associated with increased maternal morbidity, mortality, and health care costs. The long-term goal of the proposed project is to understand the factors contributing to the high c-section rate, with special emphasis on identification of potentially modifiable risk factors. It has been suggested that epidural anesthesia may increase c-sections by increasing the prevalence of fetal occiput posterior (OP) position at delivery. This fetal malposition, which is associated with a high risk of c-section, is present at delivery more frequently among women with epidural anesthesia. This suggests that either epidural anesthesia directly contributes to persistence of OP position or that women with OP fetuses receive epidural anesthesia more frequently. The proposed study is intended to distinguish between these alternative explanations and to quantify the contribution of epidural anesthesia to the persistence of OP position and c-section. Three-thousand low risk, nulliparous women, in spontaneous labor will be screened. Fetal position will be determined by ultrasonography at admission, at the time of administration of epidural anesthesia, if used, and at the time of full dilation. The position of the infant at delivery will be noted by the practitioner. Crude rate ratios and 95% confidence intervals will be calculated. Multiple logistic regression analysis will be used to adjust for confounding. The investigators state that this project is designed to determine whether epidural anesthesia is responsible for an increased persistence of OP fetal position at delivery. If epidural anesthesia does increase the prevalence of OP position at delivery, then its use could be associated with over 19,000 excess c-sections in women with OP fetuses; this could account for an additional $50 million in health care costs annually. The investigators further state that demonstration of this association would provide the first documentation of a mechanism by which epidural anesthesia affects the course of labor.